Visualizing Hg2+ ions in living cells using a FRET-based fluorescent sensor

A novel FRET fluorescent sensor for Hg2+ imaging in living cells is rationally designed based on a coumarin–rhodamine platform. RBC1 exhibit high selectivity and excellent sensitivity in both absorbance and fluorescence detection of Hg2+ in aqueous solution. After addition of increasing concentrations of Hg2+, it result in the decrease of coumarin emission at 467 nm and a new emission profile of rhodamine at 590 nm gradually increased. The response time to Hg2+ is less than 2 min, and other metal ions including Fe2+, Mn2+, Ni2+, Co2+, Cu2+, Zn2+, Cd2+, Pb2+, and Cr3+ had no interference. In addition, fluorescent imaging of Hg2+ in A375 cells is also successfully demonstrated. The design strategy of two fluorophores switching in this work would help to extend the development of FRET fluorescent sensors.

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► A novel sensor RBC1 is developed based on the coumarin–rhodamine platform.
► The sensor produce a large emission wavelength shift (123 nm).
► RBC1 achieve a lower detection limit (∼0.42 ppb).
► The sensor exhibit both colorimetric and fluorescent response to Hg2+.
► It can be used for ratiometric detecting changes in intracellular Hg2+ levels.